Design: A retrospective cohort study.

Setting: Tertiary referral centre.

Patients or Participants: Patients were diagnosed with CSP over 8 weeks of gestation and serum 𝛽-HCG≥ 5000mIU/ml.

Interventions: Intra-gestational injection of MTX followed by laparoscopic or hysteroscopic resection of CSPs.

Measurements and Main Results: A total of 378 admissions were included from 2011 to 2020. The patients were divided into 5 groups according to the interval between MTX pretreatment and surgery, group A: 1 to 4 days, group B: 5 to 7 days, group C: 8 to 10 days, group D: 11 to 14 days, group E: more than 14 days. The success rates of combine therapy in group A and group B were 93.94% and 95.57%, respectively (P > 0.05), which were statistically higher than those of group C, D and E (84.93%, 84.85%, 81.67%; all P > 0.05), all P < 0.05. With the prolongation of the interval between MTX pretreatment and surgery, the length of hospital stay was increased (all P < 0.05). The varied ranges and percentage changes of serum 𝛽-HCG before surgery were increased 1 to 4 days after MTX pretreatment, and then decreased stepwise with increasing pretreatment time (all P < 0.05).

Conclusion: Intra-gestational MTX within 7 days follewd by surgery to treat CSP patients over 8 weeks of gestation, with higher success rate and shorter hospital stay, is a more proper combined treatment modality. Within 7 days after intra-gestational MTX, the decrease of serum 𝛽-HCG has no significant effect on the success rate, and there is no need to wait for a significant decrease in serum 𝛽-HCG before surgery.